1. Field of the Invention
The invention relates to tensioning devices for use on sewing machines.
2. Description of the Prior Art
It is necessary for the proper formation of stitches on a sewing machine, that an operator be able to adjust the tension of the sewing thread. The required tension varies according to the type of sewing which is to be performed as well as the weight of thread to be used, and must be variable over a wide range. However, the thread tensioning devices commonly provided on sewing machines are incapable of setting thread tensions at the upper end of the required range because of necessary physical limitations imposed on the operation of input controls on such devices.
It is a prime object of the present invention to increase the tension selecting capability of thread tensioning devices for sewing machines.
It is another object of the invention to increase the tension selecting range of a sewing machine thread tensioning device on which the rotation of the input control is limited to not more than one complete revolution.
It is also an object of the invention to increase the upper limit of the tension selecting capability of a thread tensioning device for a sewing machine without affecting the sensitivity of the device in a low tension selecting range.
Other objects and advantages of the invention will become apparent during a reading of the specification taken in conjunction with the accompanying drawings.